"The criticism that (the government) is manipulating the currency rate is completely off the mark," Aso was quoted as saying in the online edition of the leading Nikkei business daily.

His comments were the latest in a simmering row over Japan's currency, with critics saying Tokyo's pressure on the central bank for aggressive policy action amounted to meddling that could spark a global currency war.

On Tuesday, the Bank of Japan announced an open-ended easing plan and the adoption of a two-percent inflation target to stoke growth in the deflation-plagued economy. The move was widely seen as the central bank bowing to political pressure.

"I will admit I am not without some concern about Japan right now," Merkel told top business and political leaders at the World Economic Forum in Davos on Thursday.

The German leader added that "political influences or manipulations of the exchange rate" have become a hot topic within the G20 club of leading industrialised nations.

The yen hit record highs against the dollar in late 2011 -- sitting around 75 to the greenback -- and remained strong through much of last year, hammering Japanese exporters by making their products less competitive overseas.

But it has tumbled in recent months, since opposition leader Shinzo Abe promised before December's election that he would urge the bank to be more aggressive in its battle to save the economy.

Abe swept to power in the poll and has since moved to bring BoJ policies into line with his new government's position.

In Tokyo forex trading Friday, the dollar bought 90.50 yen, against 90.40 yen in New York, while the euro fetched 120.92 yen against 120.91 yen.